WO2020246218A1

WO2020246218A1 - Rubber composition and tire

Info

Publication number: WO2020246218A1
Application number: PCT/JP2020/019428
Authority: WO
Inventors: 健介鷲頭
Original assignee: 住友ゴム工業株式会社
Priority date: 2019-06-04
Filing date: 2020-05-15
Publication date: 2020-12-10
Also published as: CN113474181A; JPWO2020246218A1; EP3904117A4; US20220235209A1; CN113474181B; EP3904117A1

Abstract

The purpose of the present invention is to provide a rubber composition and a tire which are capable of improving the overall performance of wet grip performance and dry grip performance. The present invention pertains to a rubber composition in which the hardness is reversibly changed by water, and which satisfies expressions (1) and (2) below. (1) [(Hardness when dry) - (Hardness when wet from water)] ≥ 1 (In the expression, hardness is defined as the JIS-A hardness of the rubber composition at 25℃.) (2) (tanδ at 70℃ when dry) ≥ 0.18 (In the expression, tanδ at 70℃ is defined as the loss tangent measured under the conditions of 70℃, an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz.)

Description

Rubber composition and tires

The present invention relates to rubber compositions and tires.

In recent years, as a common issue for automobiles, awareness of safety has been increasing, and further improvement of wet grip performance is required. So far, various studies have been conducted to improve wet grip performance, and many inventions of rubber compositions containing silica have been reported (for example, Patent Document 1). Since the wet grip performance is greatly affected by the performance of the rubber composition of the tread portion in contact with the road surface, technical improvements of the rubber composition for tires such as treads have been widely studied and put into practical use.

Japanese Unexamined Patent Publication No. 2008-285524

As a result of diligent studies by the present inventor, the wet grip performance of the tire has been greatly improved by the technical improvement of the rubber composition for tread using silica, but the dry road surface to the wet road surface or the wet road surface to the dry It was found that the change in grip performance when the road surface changes to the road surface remains as an important technical issue and there is room for improvement.
As a result of diligent studies by the present inventor on this point, the hardness of conventional rubber does not change when it changes from a dry state not wet with water to a so-called wet state wet with water, or it is cooled by water. It has been found that the contact area with the road surface is reduced due to the property of becoming hard, and as a result, the wet grip performance tends to be lower than the dry grip performance.
As described above, it has been found that there is room for improvement in the conventional technique in terms of improving the overall performance of wet grip performance and dry grip performance.
An object of the present invention is to provide a rubber composition and a tire capable of solving the above problems and improving the overall performance of wet grip performance and dry grip performance.

The present invention relates to a rubber composition whose hardness is reversibly changed by water and satisfies the following formulas (1) and (2).
Hardness when dried-Hardness when wet with water ≥ 1 (1)
(In the formula, the hardness is the JIS-A hardness of the rubber composition at 25 ° C.).
70 ° C tan δ ≧ 0.18 when dry (2)
(In the equation, tan δ at 70 ° C is the loss tangent measured under the conditions of 70 ° C, initial strain 10%, dynamic strain 2%, and frequency 10 Hz.)

In the above formula (1), the hardness when dried-the hardness when wet with water is preferably 2 or more, more preferably 3 or more, and further preferably 4 or more.

In the above formula (2), the tan δ at 70 ° C. at the time of drying is preferably 0.19 or more, more preferably 0.20 or more, and further preferably 0.21 or more.

The rubber composition preferably contains a hydrophilic material.

The rubber composition preferably contains a diene-based rubber and a polymer having a carbon-carbon double bond and a heteroatom.

It is preferable that the hetero atom is at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, a phosphorus atom, and a halogen atom.

When 1 g of the polymer is suspended in 10 mL of water, the insoluble content is preferably 5% by mass or more.

When 1 g of the above polymer is suspended in 10 mL of tetrahydrofuran, the insoluble content is preferably 5% by mass or more.

The rubber composition preferably contains 5 parts by mass or more of the polymer with respect to 100 parts by mass of the rubber component.

The rubber composition preferably contains an isoprene-based rubber.

The rubber composition preferably contains a butadiene rubber.

The rubber composition preferably contains 95% by mass or less of styrene-butadiene rubber in 100% by mass of the rubber component.

Styrene-butadiene rubber content in 100% by mass of rubber component> 50% by mass> Content of butadiene rubber in 100% by mass of rubber component> Isoprene-based rubber content in 100% by mass of rubber component can be satisfied. preferable.

It is preferable that silica and carbon black are each contained in an amount of 20 parts by mass or more with respect to 100 parts by mass of the rubber component.

It preferably contains a petroleum-based resin.

The rubber composition is preferably a rubber composition for tread.

The present invention also relates to a tire having a tire member that is at least partially composed of the rubber composition.

It is preferable that the tire member is a tread.

It is preferable that the tire member is a tread and the thickness of the tread is 4 mm or more.

It is preferable that the tire member is a tread and the land ratio of the tread is 30% or more.

It is preferable that the tire member is a tread and is provided with a groove continuous in the tire circumferential direction and / or a groove discontinuous in the tire circumferential direction.

According to the present invention, since the rubber composition reversibly changes its hardness with water and satisfies the above formulas (1) and (2), the total performance of wet grip performance and dry grip performance can be improved.

The hardness of the rubber composition of the present invention changes reversibly with water and satisfies the following formulas (1) and (2). As a result, the overall performance of wet grip performance and dry grip performance can be improved.
Hardness when dried-Hardness when wet with water ≥ 1 (1)
(In the formula, the hardness is the JIS-A hardness of the rubber composition at 25 ° C.).
70 ° C tan δ ≧ 0.18 when dry (2)
(In the equation, tan δ at 70 ° C is the loss tangent measured under the conditions of 70 ° C, initial strain 10%, dynamic strain 2%, and frequency 10 Hz.)

The rubber composition can obtain the above-mentioned effects, but the reason why such effects are obtained is not always clear, but it is presumed as follows.
The hardness of the rubber composition of the present invention changes reversibly with water and satisfies the above formula (1). Here, the above formula (1) means that the hardness when wet with water is smaller than the hardness when wet. That is, the hardness of the rubber composition of the present invention changes reversibly with water and satisfies the above formula (1), but the hardness when wet with water is smaller than the hardness when wet. It also means that the hardness changes reversibly with the presence of water.
Therefore, when the road surface changes from a dry road surface to a wet road surface, the rubber composition is moistened with water, the hardness of the rubber composition decreases, the decrease in grip performance (wet grip performance) can be suppressed, and good grip performance (wet grip performance) can be suppressed. ) Is obtained. This is because it is easy to slip on a wet road surface, so sufficient grip performance cannot be obtained with the hardness suitable for a dry road surface, but as the hardness decreases, the contact area with the road surface increases and the grip performance (wet). It is presumed that a decrease in grip performance (grip performance) can be suppressed and good grip performance (wet grip performance) can be obtained.
On the other hand, when the road surface changes from a wet road surface to a dry road surface, the rubber composition moistened with water is dried, the hardness of the rubber composition increases, the decrease in grip performance (dry grip performance) can be suppressed, and good grip performance (good grip performance). Dry grip performance) can be obtained. This is because it is difficult to slip on a dry road surface, so sufficient grip performance cannot be obtained with the hardness suitable for a wet road surface, but as the hardness increases, the hardness becomes suitable for a dry road surface, and the grip performance (dry grip). It is presumed that the deterioration of performance) can be suppressed and good grip performance (dry grip performance) can be obtained.
In this way, the hardness is reversibly changed by water, and by satisfying the above formula (1), an appropriate hardness can be obtained according to the water condition of the road surface (wet road surface, dry road surface). The overall performance of grip performance and dry grip performance can be improved.
Further, the rubber composition of the present invention can obtain better wet grip performance and dry grip performance by satisfying the above formula (2).
Therefore, the hardness of the rubber composition of the present invention is reversibly changed by water, and by satisfying the above formulas (1) and (2), the total performance of wet grip performance and dry grip performance can be improved.
As described above, the present invention solves the problem (objective) of improving the overall performance of wet grip performance and dry grip performance by forming a rubber composition that satisfies the parameters of the above formulas (1) and (2). Is what you do. That is, the parameter does not define a problem (purpose), and the problem of the present application is to improve the overall performance of wet grip performance and dry grip performance, and as a solution for that, the rubber composition is used in the above formula (1). ) And (2) are satisfied. That is, it is an indispensable constituent requirement to satisfy the parameters of the above equations (1) and (2).
In the present specification, the hardness of the rubber composition, tan δ, means the hardness of the rubber composition after vulcanization, tan δ. Further, tan δ is a value obtained by conducting a viscoelasticity test on the vulcanized rubber composition.

In the present specification, the reversible change in hardness due to water means that the hardness of the rubber composition (after vulcanization) is reversibly increased or decreased due to the presence of water. It should be noted that, for example, the hardness may change reversibly when the hardness changes from drying to water wetting to drying, and the hardness does not have to be the same during the first drying and the subsequent drying. Alternatively, the hardness may be the same at the time of the first drying and the time of the later drying.

In the present specification, the hardness at the time of drying means the hardness of the rubber composition (after vulcanization) in a dry state, and specifically, the rubber composition dried by the method described in Examples (the rubber composition). It means the hardness after vulcanization).
In the present specification, the hardness when moistened with water means the hardness of the rubber composition (after vulcanization) in a state of being moistened with water, and specifically, by the method described in Examples, with water. It means the hardness of the wet rubber composition (after vulcanization).

In the present specification, the hardness (JIS-A hardness) of the rubber composition (after vulcanization) is defined in "Vulcanized rubber and thermoplastic rubber-How to determine hardness-Part 3:" of JIS K6253-3 (2012). Durometer hardness is measured by a Type A durometer at 25 ° C.

In the present specification, the tan δ at 70 ° C. at the time of drying means the tan δ at 70 ° C. of the rubber composition (after vulcanization) in a dry state, and specifically, by the method described in Examples. It means tan δ at 70 ° C. of the dried rubber composition (after vulcanization).

In the present specification, 70 ° C. tan δ of the rubber composition (after vulcanization) is a loss tangent measured under the conditions of 70 ° C., initial strain of 10%, dynamic strain of 2%, and frequency of 10 Hz.

As shown in the above formula (1) (hardness when dried-hardness when wet with water (hardness of rubber composition when dry (after vulcanization) -hardness of rubber composition when wet with water (after vulcanization))) Is 1 or more, preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, particularly preferably 5 or more, most preferably 6 or more, more preferably 8 or more, more preferably 9 or more, more preferably. It is 10 or more, more preferably 11 or more, more preferably 13 or more, more preferably 15 or more, more preferably 18 or more, more preferably 21 or more, more preferably 24 or more, and the upper limit is not particularly limited, but is preferable. It is 50 or less, more preferably 40 or less, still more preferably 30 or less, particularly preferably 28 or less, and most preferably 26 or less. When it is within the above range, the effect can be obtained more preferably.

The hardness at the time of drying (hardness of the rubber composition (after vulcanization) at the time of drying) can be appropriately adjusted within a range satisfying the above formula (1), but is preferably 20 or more, more preferably 25 or more, and further. It is preferably 30 or more, particularly preferably 40 or more, most preferably 50 or more, more preferably 55 or more, more preferably 58 or more, more preferably 62 or more, more preferably 64 or more, and preferably 95 or less. It is more preferably 90 or less, still more preferably 85 or less, particularly preferably 75 or less, most preferably 70 or less, more preferably 66 or less, and even more preferably 65 or less. When the hardness is within the above range, the effect is more preferably obtained.

The hardness when wetted with water (hardness of the rubber composition (after vulcanization) when wetted with water) can be appropriately adjusted within a range satisfying the above formula (1), but is preferably 20 or more, more preferably 25 or more. More preferably 30 or more, particularly preferably 35 or more, most preferably 40 or more, more preferably 43 or more, more preferably 45 or more, more preferably 46 or more, more preferably 49 or more, more preferably 50 or more, more. It is preferably 51 or more, more preferably 53 or more, more preferably 55 or more, and preferably 80 or less, more preferably 70 or less, still more preferably 65 or less, still more preferably 62 or less, and particularly preferably 61 or less. It is most preferably 60 or less, more preferably 59 or less, and more preferably 56 or less. When the hardness is within the above range, the effect is more preferably obtained.

As shown in the above formula (2), the tan δ at 70 ° C. at the time of drying (tan δ at 70 ° C. of the rubber composition (after vulcanization) at the time of drying) is 0.18 or more, preferably 0.19 or more, more preferably. Is 0.20 or more, more preferably 0.21 or more, particularly preferably 0.22 or more, most preferably 0.23 or more, and the upper limit is not particularly limited, but is preferably 0.60 or less, more preferably 0. It is .40 or less, more preferably 0.30 or less, and particularly preferably 0.25 or less. When it is within the above range, the effect can be obtained more preferably.

The hardness change represented by the above formula (1) and the reversible hardness change due to water of the rubber composition are reversible molecular bonds such as hydrogen bond and ionic bond to the hydrophilic material, that is, water. Can be achieved by blending a compound capable of
The hydrophilic material is not particularly limited as long as it is a compound capable of reversible molecular bonds such as hydrogen bond and ionic bond with respect to water, and examples thereof include compounds having a hetero atom.
More specifically, the production guideline for satisfying the above parameters will be described. By using a rubber component containing a diene-based rubber and a polymer having a carbon-carbon double bond and a heteroatom in combination, the above formula of a rubber composition can be described. The hardness change represented by (1) and the reversible hardness change due to water can be realized.
This is because the heteroatom is capable of reversible molecular bonds such as hydrogen bonds and ionic bonds with respect to water in the rubber composition, and as a result of the formation of these molecular bonds, the rubber composition when wetted with water. This is because the hardness of the object decreases.
Furthermore, by the above combined use, the polymer is crosslinked to the rubber component by a carbon-carbon double bond during vulcanization and fixed to the rubber component, so that the release of the polymer from the rubber component can be suppressed and the rubber surface can be pressed. Precipitation of the polymer can be suppressed, and deterioration of grip performance (wet grip performance, dry grip performance) can also be suppressed.

Further, the tan δ at 70 ° C. at the time of drying depends on the type and amount of chemicals (particularly rubber components, fillers, softeners, resins, sulfur, vulcanization accelerators, silane coupling agents) blended in the rubber composition. It is possible to adjust, for example, using a softener (for example, resin) that is less compatible with the rubber component, using non-modified rubber, increasing the amount of filler, oil as a plasticizer. The tan δ at 70 ° C. tends to increase when the amount of rubber is increased, the amount of sulfur is reduced, the amount of vulcanization accelerator is reduced, or the amount of silane coupling agent is reduced.

Further, the hardness at the time of drying can be adjusted by the type and amount of chemicals (particularly, softeners such as rubber components, fillers, oils and resins) blended in the rubber composition. For example, the softening agent. When the amount of rubber is increased, the hardness at the time of drying tends to decrease, when the amount of the filler is increased, the hardness at the time of drying tends to increase, and when the amount of sulfur is decreased, the hardness at the time of drying tends to decrease. The hardness at the time of drying can also be adjusted by adjusting the blending amount of sulfur and the vulcanization accelerator. More specifically, increasing the amount of sulfur tends to increase the hardness during drying, and increasing the amount of vulcanization accelerator tends to increase the hardness during drying.

More specifically, after adjusting the hardness at the time of drying within a desired range, a hydrophilic material is blended, more preferably a rubber component containing a diene rubber, a carbon-carbon double bond and a hetero. By using the rubber composition in combination with a polymer having an atom, it is possible to realize a hardness change represented by the above formula (1) and a reversible hardness change due to water, and the tan δ at 70 ° C. during drying is also in a desired range. It becomes possible to adjust within. Further, the amount of the filler may be increased for the purpose of increasing the tan δ at 70 ° C. during drying.

As another means for achieving the hardness change represented by the above formula (1) and the reversible hardness change due to water of the rubber composition, a rubber component containing a diene rubber, a carbon-carbon double bond and a hetero atom are used. When the polymer is used in combination with a polymer having the above, the polymer is crosslinked to the rubber component by a carbon-carbon double bond and fixed to the rubber component during brewing, so that the release of the polymer from the rubber component can be suppressed. The hardness change represented by the above formula (1) of the rubber composition and the reversible hardness change due to water can be achieved.
If it does not have a carbon-carbon double bond, the rubber composition may be liberated into water when it comes into contact with water, and a reversible change in hardness may not be obtained.

As another means for achieving the hardness change represented by the above formula (1) and the reversible hardness change due to water of the rubber composition, for example, the ionic bond between the rubber molecules is added and dried by adding water. Examples thereof include a method of reversibly cutting and recombining. More specifically, by using a rubber having halogen or oxygen and a compound having metal, metalloid or nitrogen in combination, the hardness change represented by the above formula (1) of the rubber composition is reversible by water. Hardness change can be realized. This is because, by the combined use, an ionic bond is formed between rubber molecules by a cation derived from a metal, a semimetal or nitrogen, and an anion derived from halogen or oxygen, and an ionic bond is formed between the rubber molecules by adding water. This is because as a result of cleavage and recombination of ionic bonds due to drying of water, hardness decreases when wet with water and increases when dried.

The chemicals that can be used will be described below.

Examples of the rubber component include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like. Diene rubber can be mentioned. The rubber component may be used alone or in combination of two or more. Of these, diene-based rubber is preferable, isoprene-based rubber, BR, and SBR are more preferable, and SBR is even more preferable. The combined use of isoprene-based rubber and SBR, the combined use of BR and SBR, and the combined use of isoprene-based rubber, BR and SBR are also preferable.

Here, the rubber component preferably has a weight average molecular weight (Mw) of 150,000 or more, and more preferably 350,000 or more. The upper limit of Mw is not particularly limited, but is preferably 4 million or less, more preferably 3 million or less.

The content of the diene rubber in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 50% by mass or more, further preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass. It is mass% or more, and may be 100 mass%. Within the above range, the effect tends to be better obtained.

The SBR is not particularly limited, and for example, emulsion polymerization SBR (E-SBR), solution polymerization SBR (S-SBR), and the like, which are common in the tire industry, can be used. These may be used alone or in combination of two or more.

The amount of styrene in SBR is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably. Is 30% by mass or less. Within the above range, the effect tends to be obtained more preferably.

The vinyl content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, particularly preferably 40% by mass or more, most preferably 50% by mass or more, and preferably. Is 75% by mass or less, more preferably 65% by mass or less. Within the above range, the compatibility with BR becomes good, and the effect tends to be obtained more preferably.

The SBR may be a non-modified SBR or a modified SBR.
The modified SBR may be an SBR having a functional group that interacts with a filler such as silica. For example, at least one end of the SBR is modified with a compound having the above functional group (modifying agent). SBR (terminal modified SBR having the above functional group at the end), main chain modified SBR having the above functional group on the main chain, and main chain terminal modified SBR having the above functional group on the main chain and the end (for example, on the main chain) Main chain terminal modified SBR having the above functional group and having at least one end modified with the above modifying agent) or a polyfunctional compound having two or more epoxy groups in the molecule, which is modified (coupling) with a hydroxyl group. And terminally modified SBR into which an epoxy group has been introduced. These may be used alone or in combination of two or more.

Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group and a disulfide. Examples thereof include a group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group and an epoxy group. .. In addition, these functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is replaced with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxy group having 1 to 6 carbon atoms). An alkoxysilyl group having 1 to 6 carbon atoms) and an amide group are preferable.

As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Zeon Corporation, etc. can be used.

The content of SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 95% by mass or less. It is 90% by mass or less, more preferably 80% by mass or less. Within the above range, the effect tends to be better obtained.

The BR is not particularly limited, and a BR commonly used in the tire industry can be used. These may be used alone or in combination of two or more.

The cis amount of BR is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 97% by mass or more. The upper limit is not particularly limited and may be 100% by mass. Within the above range, the effect tends to be obtained more preferably.

The BR may be either a non-modified BR or a modified BR. Examples of the modified BR include modified BRs into which the above-mentioned functional groups have been introduced. The preferred embodiment is the same as for the modified SBR.

As the BR, for example, products such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and ZEON Corporation can be used.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 70% by mass or less, more preferably 40% by mass or less, still more preferably. It is 30% by mass or less. Within the above range, the effect tends to be obtained more preferably.

Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR and the like. As the NR, for example, SIR20, RSS # 3, TSR20 and the like, which are common in the tire industry, can be used. The IR is not particularly limited, and for example, an IR 2200 or the like that is common in the tire industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., and modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber and the like. These may be used alone or in combination of two or more. Of these, NR is preferable.

The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 3% by mass or more, more preferably 5% by mass or more, and preferably 60% by mass or less, more preferably 30% by mass or less, and further. It is preferably 20% by mass or less. Within the above range, the effect tends to be obtained more preferably.

Styrene-butadiene rubber content in 100% by mass of rubber component> 50% by mass> Content of butadiene rubber in 100% by mass of rubber component> Isoprene-based rubber content in 100% by mass of rubber component can be satisfied. preferable. As a result, the effect tends to be obtained more preferably.

In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are gel permeation chromatographs (GPC) (GPC-8000 series manufactured by Toso Co., Ltd., detector: differential refractometer, column: It can be obtained by standard polystyrene conversion based on the measured value by TSKGEL SUPERMULTIPORE HZ-M manufactured by Toso Co., Ltd.
The amount of cis (cis-1,4-bonded butadiene unit amount) and vinyl amount (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis, and the amount of styrene is measured by ¹ H-NMR. Can be measured by.

The rubber composition preferably contains a hydrophilic material.
As described above, the hydrophilic material is not particularly limited as long as it is a compound capable of reversible molecular bonds such as hydrogen bond and ionic bond with respect to water, and examples thereof include compounds having a hetero atom. .. Among them, a compound having a carbon-carbon double bond and a heteroatom is preferable, and a polymer having a carbon-carbon double bond and a heteroatom is more preferable.

The carbon-carbon double bond is necessary for cross-linking with the diene rubber, and the number thereof is not particularly limited.

The hetero atom means an atom other than a carbon atom and a hydrogen atom, and a reversible molecular bond such as a hydrogen bond or an ionic bond with respect to water is not particularly limited as much as possible, but an oxygen atom, a nitrogen atom and a silicon atom. , Sulfur atom, phosphorus atom, and halogen atom are preferably at least one selected from the group, oxygen atom, nitrogen atom, and silicon atom are more preferable, and oxygen atom is further preferable. The hetero atom is preferably present in the main chain (skeleton) of the polymer, and more preferably in the repeating unit of the polymer.

Examples of the structure and group containing an oxygen atom include an ether group, an ester, a carboxy group, a carbonyl group, an alkoxy group, and a hydroxy group. Of these, an ether group is preferable, and an oxyalkylene group is more preferable.
Examples of the structure and group containing a nitrogen atom include an amino group (primary amino group, secondary amino group, tertiary amino group), amide group, nitrile group, nitro group and the like. Of these, an amino group is preferable, and a tertiary amino group is more preferable.
Examples of the structure and group containing a silicon atom include a silyl group, an alkoxysilyl group, and a silanol group. Of these, a silyl group is preferable, and an alkoxysilyl group is more preferable.
Examples of the structure and group containing a sulfur atom include a sulfide group, a sulfate group, a sulfate ester, and a sulfo group.
Examples of the structure and group containing a phosphorus atom include a phosphoric acid group and a phosphoric acid ester.
Examples of the structure and group containing a halogen atom include a halogeno group such as a fluoro group, a chloro group, a bromo group and an iodine group.

The oxyalkylene group is a group represented by − (AO) −, and preferably a group represented by − (AO) _n − (n is the number of repeating units).
The carbon number of the alkylene group A in the oxyalkylene group AO is preferably 1 or more, more preferably 2 or more, preferably 10 or less, more preferably 8 or less, still more preferably 6 or less. Within the above range, the effect tends to be obtained more preferably.

The alkylene group A in the oxyalkylene group AO may be linear or branched, but the branched form is preferable because it has a bulkier structure and the effect can be obtained more preferably.
The AO is branched into an oxyalkylene group having 2 to 3 carbon atoms (oxyethylene group (EO), an oxypropylene group (PO)) and an oxyalkylene group having 2 to 3 carbon atoms because the effect can be obtained more preferably. It is preferably a group to which the chain R ⁴ (R ⁴ represents a hydrocarbon group which may have a hetero atom) is bonded, an oxyalkylene group having 2 to 3 carbon atoms and an oxy having 2 to 3 carbon atoms. it is more preferable to use branched R ⁴ is bonded group to an alkylene group. Note that branched chain R ⁴ is preferably attached to a carbon atom adjacent to the oxygen atom.

The hydrocarbon group that may have a heteroatom of R ⁴ is not particularly limited. The number of carbon atoms of the hydrocarbon group is preferably 1 or more, more preferably 2 or more, preferably 10 or less, more preferably 6 or less, still more preferably 4 or less. Within the above range, the effect tends to be obtained more preferably.
As the hydrocarbon group which may have a hetero atom of R ⁴ , a group represented by the following formula is preferable.

The group represented by − (AO) − is more preferably a group represented by the following formula (B), and particularly preferably a group represented by the following formulas (A) to (B). A group represented by the following formula (C) can also be used in combination.

When the polymer contains two or more oxyalkylene groups, the arrangement of the oxyalkylene groups may be block or random.

As the polymer, a polymer containing a group (structural unit) represented by the above formula (B) is preferable, and a polymer composed of a group (structural unit) represented by the above formulas (A) to (B) is more preferable. preferable.
The content of the group (structural unit) represented by the above formula (B) in 100 mol% of the polymer is preferably 2 mol% or more, more preferably 5 mol% or more, preferably 50 mol% or less, more preferably 40 mol. % Or less, more preferably 30 mol% or less, and particularly preferably 20 mol% or less.

The weight average molecular weight (Mw) of the polymer is preferably 10,000 or more, more preferably 50,000 or more, still more preferably 100,000 or more, particularly preferably 500,000 or more, preferably 3 million or less, more preferably 250. It is 10,000 or less, more preferably 2 million or less, particularly preferably 1.5 million or less, and most preferably 1 million or less.

The insoluble content (water-insoluble content) of the above polymer when 1 g is suspended is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 30% by mass or more, based on 10 mL of water. It is particularly preferably 50% by mass or more, most preferably 70% by mass or more, more preferably 80% by mass or more, still most preferably 90% by mass or more, and the upper limit is not particularly limited.
The insoluble matter can be measured by the method described in Examples.
The larger the amount of the insoluble matter, the more the amount of the polymer eluted in water when the rubber is wetted with water, and the reversible change in hardness can be more preferably achieved.

The insoluble content (THF insoluble content) of the above polymer when 1 g is suspended is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 30% by mass or more, based on 10 mL of tetrahydrofuran. It is particularly preferably 50% by mass or more, most preferably 70% by mass or more, more preferably 90% by mass or more, and the upper limit is not particularly limited.
The insoluble matter can be measured by the method described in Examples.
Since the diene rubber has solubility in tetrahydrofuran, the larger the insoluble content of the polymer in tetrahydrofuran, the more the effect of lowering the hardness at the time of water wetting tends to be sufficiently obtained without being compatible with the diene rubber.

The above polymer may be a commercially available product, or may be produced by preparing a polymer from a monomer having a hetero atom.
The monomer having a hetero atom is not particularly limited, but examples of the monomer having an oxygen atom include ethers such as vinyl ether, alkoxystyrene, allylglycidyl ether, ethylene oxide, propylene oxide, and tetrahydrofuran, (meth). ) Acrylic acids and their esters, acid anhydrides, monomers having a nitrogen atom include acrylonitrile, N-vinylcarbazole, carbamate, caprolactam, and monomers having a silicon atom include alkoxysilylstyrene and alkoxysilylvinyls. Can be mentioned.
When the monomer having a heteroatom does not contain an unsaturated bond, the monomer having a heteroatom and the monomer having a carbon-carbon double bond (for example, a conjugated diene monomer such as butadiene and isoprene, and a vinyl polymer such as styrene) ) May be polymerized.
The polymerization method is not particularly limited, and a known method can be used.

The content of the polymer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and most preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. 40 parts by mass or more, more preferably 50 parts by mass or more, further most preferably 60 parts by mass or more, particularly most preferably 70 parts by mass or more, more preferably 80 parts by mass or more, more preferably 90 parts by mass or more, more preferably. Is 100 parts by mass or more, preferably 150 parts by mass or less, and more preferably 120 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition may contain silica.
Examples of silica include dry silica (silicic anhydride) and wet silica (hydrous silicic acid), but wet silica is preferable because it contains a large amount of silanol groups. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is 40 m ² / g or more, preferably 60 m ² / g or more, more preferably 80 m ² / g or more, and further preferably 160 m ² / g or more. The N ₂ SA is preferably 600 m ² / g or less, more preferably 300 m ² / g or less, still more preferably 250 m ² / g or less, and particularly preferably 200 m ² / g or less. Within the above range, the effect tends to be obtained more preferably.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-81.

As the silica, for example, products such as Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation can be used.

The content of silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, particularly preferably 20 parts by mass or more, and most preferably 30 parts by mass with respect to 100 parts by mass of the rubber component. It is more than parts by mass, more preferably 50 parts by mass or more, more preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and preferably 150 parts by mass or less, more preferably 140 parts by mass or less, still more preferably. It is 120 parts by mass or less, particularly preferably 100 parts by mass or less, and most preferably 90 parts by mass or less. Within the above range, the effect tends to be better obtained.

In the rubber composition, the content of silica in 100% by mass of the filler (reinforcing filler) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more. The upper limit is not particularly limited, but is preferably 90% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less. Within the above range, the effect tends to be obtained more preferably.

When the rubber composition contains silica, it is preferable to further contain a silane coupling agent.
The silane coupling agent is not particularly limited, and for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-Triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) ) Disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3- Sulfates such as triethoxysilylpropylmethacrylate monosulfide, mercaptos such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyls such as vinyltriethoxysilane and vinyltrimethoxysilane, 3-amino Amino series such as propyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy series such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, 3-nitropropyltrimethoxysilane, Examples thereof include nitro type such as 3-nitropropyltriethoxysilane and chloro type such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, for example, products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd. can be used. These may be used alone or in combination of two or more. Of these, sulfide-based silane coupling agents and mercapto-based silane coupling agents are preferable because the effects tend to be better, and disulfide-based agents having a disulfide bond such as bis (3-triethoxysilylpropyl) disulfide are preferable. Silane coupling agents are more preferred.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, based on 100 parts by mass of silica. Is. Within the above range, the effect tends to be better obtained.

The rubber composition may contain carbon black.
The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, more preferably 100 m ² / g or more, and preferably 150 m ² / g or less, more preferably 130 m ² / g. It is as follows. Within the above range, the effect tends to be better obtained.
In this specification, N ₂ SA of carbon black is a value measured in accordance with JIS K6217-2: 2001.

As carbon black, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. Can be used.

The content of carbon black is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more, based on 100 parts by mass of the rubber component. It is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, further preferably 80 parts by mass or less, particularly preferably 60 parts by mass or less, and most preferably 50 parts by mass or less. Within the above range, the effect tends to be better obtained.

It is preferable that silica and carbon black are contained in an amount of 20 parts by mass or more with respect to 100 parts by mass of the rubber component, and it is more preferable that silica and carbon black are contained in an amount of 30 parts by mass or more with respect to 100 parts by mass of the rubber component. Within the above range, the effect tends to be better obtained.

The rubber composition may contain oil.
Examples of the oil include process oils, vegetable oils and fats, or mixtures thereof. As the process oil, for example, paraffin-based process oil, aroma-based process oil, naphthenic process oil, and the like can be used. Vegetable oils and fats include castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, rosin, pine oil, pineapple, tall oil, corn oil, rice oil, beni flower oil, sesame oil Examples thereof include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Of these, a process oil is preferable, and an aroma-based process oil is more preferable, because a good effect can be obtained.

Examples of oils include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H & R Co., Ltd., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd. And other products can be used.

The content of the oil is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. It is preferably 35 parts by mass or less. Within the above range, the effect tends to be better obtained. The oil content also includes the amount of oil contained in rubber (oil spread rubber).

The rubber composition may contain a resin.
The resin is not particularly limited as long as it is widely used in the tire industry, and is rosin-based resin, kumaron inden resin, α-methylstyrene-based resin, terpene-based resin, pt-butylphenol acetylene resin, acrylic-based resin. Examples thereof include resin, C5 resin, and C9 resin. Commercially available products include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Ltd., Arizona Chemical Co., Ltd., Nikko Chemical Co., Ltd., Japan Co., Ltd. Products such as catalysts, JXTG Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Co., Ltd., and Toa Synthetic Co., Ltd. can be used. These may be used alone or in combination of two or more. Of these, petroleum-based resins such as kumaron inden resin, α-methylstyrene resin, pt-butylphenol acetylene resin, C5 resin, and C9 resin are preferable, and kumaron inden resin is more preferable.

The softening point of the resin is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, further preferably 80 ° C. or higher, preferably 200 ° C. or lower, more preferably 160 ° C. or lower, still more preferably 140 ° C. or lower, particularly preferably. Is 120 ° C. or lower. Within the above range, the effect tends to be more preferably obtained.
In the present specification, the softening point of the resin is the temperature at which the ball drops when the softening point defined in JIS K 6220-1: 2001 is measured by a ring-ball type softening point measuring device.

The content of the resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, particularly preferably 20 parts by mass or more, and most preferably 30 parts by mass with respect to 100 parts by mass of the rubber component. It is more than parts by mass, more preferably 40 parts by mass or more, and preferably 80 parts by mass or less, more preferably 60 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition may contain wax.
The wax is not particularly limited, and examples thereof include petroleum wax such as paraffin wax and microcrystalline wax; natural wax such as plant wax and animal wax; and synthetic wax such as a polymer such as ethylene and propylene. These may be used alone or in combination of two or more. Of these, petroleum wax is preferable, and paraffin wax is more preferable.

As the wax, for example, products such as Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Kagaku Co., Ltd. can be used.

The content of the wax is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. It is less than a part. Within the above range, the effect tends to be better obtained.

The rubber composition may contain an anti-aging agent.
Examples of the anti-aging agent include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis (α, α′-dimethylbenzyl) diphenylamine; -Isopropyl-N'-phenyl-p-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylenediamine, etc. P-Phenylenediamine-based anti-aging agent; quinoline-based anti-aging agent such as a polymer of 2,2,4-trimethyl-1,2-dihydroquinolin; 2,6-di-t-butyl-4-methylphenol, Monophenolic antioxidants such as styrenated phenol; tetrakis- [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] bis, tris, polyphenolic aging such as methane Examples include preventive agents. These may be used alone or in combination of two or more. Of these, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferable.

As the anti-aging agent, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis Co., Ltd. and the like can be used.

The content of the anti-aging agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass with respect to 100 parts by mass of the rubber component. It is less than a part. Within the above range, the effect tends to be better obtained.

The rubber composition may contain stearic acid.
As the stearic acid, conventionally known ones can be used, and for example, products such as NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd. can be used.

The content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass with respect to 100 parts by mass of the rubber component. It is as follows. Within the above range, the effect tends to be better obtained.

The rubber composition may contain zinc oxide.
Conventionally known zinc oxide can be used. For example, products of Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. Can be used.

The content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass with respect to 100 parts by mass of the rubber component. It is as follows. Within the above range, the effect tends to be better obtained.

The rubber composition may contain sulfur.
Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are generally used in the rubber industry. These may be used alone or in combination of two or more.

As the sulfur, for example, products such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexis Co., Ltd., Nippon Inui Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd. can be used.

The sulfur content is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass with respect to 100 parts by mass of the rubber component. It is less than a part, more preferably 3 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition may contain a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; tetramethylthiuram disulfide (TMTD). ), Tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram-based vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, N-tert-butyl- Sulfenamide-based vulcanization accelerators such as 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide; diphenylguanidine, Examples thereof include guanidine-based vulcanization accelerators such as dioltotrilguanidine and orthotrilbiguanidine. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferable because the effects can be obtained more preferably.

As the vulcanization accelerator, for example, products manufactured by Kawaguchi Chemical Industry Co., Ltd., Ouchi Shinko Chemical Co., Ltd., etc. can be used.

The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 7 parts by mass with respect to 100 parts by mass of the rubber component. It is as follows. Within the above range, the effect tends to be better obtained.

In addition to the above components, the rubber composition contains additives commonly used in the tire industry, such as organic peroxides; fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. ; Etc. may be further blended. The content of these additives is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition can be produced, for example, by kneading each component using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing.

As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100 to 180 ° C., preferably 120 to 170 ° C. In the final kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120 ° C. or lower, preferably 80 to 110 ° C. Further, the composition obtained by kneading the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190 ° C, preferably 150 to 185 ° C. The vulcanization time is usually 5 to 15 minutes.

The rubber composition includes, for example, tread (cap tread), sidewall, base tread, under tread, shoulder, clinch, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner and the like. It can also be used as a tire member (as a rubber composition for a tire) such as a side reinforcing layer of a run flat tire. Among them, it is preferably used for members (treads, sidewalls, shoulders) that can come into contact with water, and is more preferably used for treads. In the case of a tread composed of a cap tread and a base tread, it can be suitably used for a cap tread.
Examples of the member that may come into contact with water include a member (tread, sidewall, shoulder) located on the outermost surface of the tire when the tire is new or when the tire is worn out.

The tire of the present invention (pneumatic tire, etc.) is produced by a usual method using the above rubber composition. That is, a rubber composition containing various additives as needed is extruded according to the shape of each member of the tire (particularly, tread (cap tread)) at the unvulcanized stage, and then put onto the tire molding machine. The tire can be manufactured by heating and pressurizing in a vulcanizer after forming an unvulcanized tire by molding it by a usual method and laminating it together with other tire members.

The tire member (for example, tread) of the tire may be composed of at least a part of the rubber composition, and may be entirely composed of the rubber composition.

The above tires are passenger car tires, large passenger car tires, large SUV tires, truck / bus tires, motorcycle tires, competition tires, winter tires (studless tires, snow tires, stud tires), all-season tires, and runs. It is suitably used as a flat tire, an aircraft tire, a mining tire, and the like.

In the above tire, the thickness of the tread is preferably 4 mm or more, more preferably 6 mm or more, still more preferably 8 mm or more, and particularly preferably 11 mm or more. Within the above range, the effect tends to be better obtained. The upper limit is not particularly limited, but is preferably 35 mm or less, more preferably 25 mm or less, still more preferably 20 mm or less, and particularly preferably 15 mm or less.

In the above tire, the groove depth of the tread (distance in the tire longitudinal direction to the deepest part of the groove) is usually about 70% of the thickness of the tread, which correlates with the thickness of the tread.

The tire has a tread whose hardness is reversibly changed by water and is composed of a rubber composition satisfying the above formulas (1) and (2), and the thickness of the tread is 4 mm or more. Is preferable. As a result, the overall performance of the wet grip performance and the dry grip performance can be more preferably improved.

Although the above-mentioned tires can obtain the above-mentioned effects, the reason why such effects are obtained is not always clear, but it is presumed as follows.
As described above, the hardness is reversibly changed by water, and by satisfying the above formula (1), an appropriate hardness can be obtained according to the water condition of the road surface (wet road surface, dry road surface). The overall performance of the grip performance and the dry grip performance can be improved, and further, the rubber composition of the present invention can obtain better wet grip performance and dry grip performance by satisfying the above formula (2).
There is a correlation between the thickness of the tread and the groove depth, and the groove depth tends to increase as the thickness increases. Therefore, from the viewpoint of the thickness of the tread, the wet grip performance can be improved by increasing the groove depth of the tread, that is, increasing the thickness of the tread.
As described above, the wet grip performance of the tread is improved by increasing the thickness, but the tire has the dry grip performance and the wet grip when the thickness of the tread produced by the rubber composition is within a predetermined range. The overall performance of the grip performance can be improved more preferably.
Therefore, in the tire, the rubber composition constituting the tread changes its hardness reversibly with water, satisfies the above formulas (1) and (2), and further, the thickness of the tread is within a predetermined range. As a result, the overall performance of wet grip performance and dry grip performance can be improved more preferably.
In addition, by using rubber whose hardness changes reversibly with water, it is possible to obtain grip performance according to the road surface condition, and the range of hardness of the rubber that can be used for the tread is expanded, so the tread design The degree of freedom can be improved.

In the present specification, the thickness of the tread is the tire radial length of the portion where the width of the layer in the tire radial direction is maximum when the tread is composed of one layer, and the tread is the cap tread and the base tread. In the case of a tread having a multi-layer structure such as when composed of layers, it is the tire radial length of the portion where the width of the cap tread located on the surface layer in the tire radial direction is maximum.

In the above tire, the land ratio of the tread is preferably 30% or more, more preferably 40% or more, more preferably 50% or more, still more preferably 75% or more from the viewpoint of dry grip performance. From the viewpoint of wet grip performance, the upper limit is preferably 95% or less, more preferably 90% or less, still more preferably 85% or less.

The tire has a tread whose hardness is reversibly changed by water and is composed of a rubber composition satisfying the above formulas (1) and (2), and the land ratio of the tread is 30% or more. It is preferable to have. As a result, the overall performance of the wet grip performance and the dry grip performance can be more preferably improved.

Although the above-mentioned tires can obtain the above-mentioned effects, the reason why such effects are obtained is not always clear, but it is presumed as follows.
As described above, the hardness is reversibly changed by water, and by satisfying the above formula (1), an appropriate hardness can be obtained according to the water condition of the road surface (wet road surface, dry road surface). The overall performance of the grip performance and the dry grip performance can be improved, and further, the rubber composition of the present invention can obtain better wet grip performance and dry grip performance by satisfying the above formula (2).
Further, in the tread, the dry grip performance is improved by increasing the land ratio, and the wet grip performance is improved by decreasing the land ratio. However, in the tire, the land ratio of the tread produced by the rubber composition is predetermined. Within the range, the overall performance of dry grip performance and wet grip performance can be more preferably improved.
Therefore, in the tire, the rubber composition constituting the tread reversibly changes in hardness with water, satisfies the above formulas (1) and (2), and further, the land ratio of the tread is within a predetermined range. This makes it possible to more preferably improve the overall performance of the wet grip performance and the dry grip performance.
In addition, by using rubber whose hardness changes reversibly with water, it is possible to obtain grip performance according to the road surface condition, and the range of hardness of the rubber that can be used for the tread is expanded, so the tread design The degree of freedom can be improved.

In the present specification, when the tire is a pneumatic tire, the land ratio is calculated from the ground contact shape under normal rim, normal internal pressure, and normal load conditions. In the case of non-pneumatic tires, the same measurement can be performed without the need for regular internal pressure.
A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, TRA is a "Design Rim", or ETRTO. If there is, it means "Measuring Rim".
The "regular internal pressure" is the air pressure defined for each tire by the above standard. If it is JATTA, it is the maximum air pressure. If it is TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". If there is, it means "INFRATION PRESSURE", but in the case of passenger car tires, it is 180 kPa.
The "regular load" is the load defined for each tire by the above standard, and is the maximum load capacity for JATTA, and the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFRATION PRESSURES" for TRA, ETRTO. If so, it means a load obtained by multiplying "LOAD CAPACITY" by 0.88, respectively.
For the ground contact shape, assemble it on a regular rim, apply regular internal pressure, let it stand at 25 ° C for 24 hours, then apply black ink on the tire tread surface, apply a regular load and press it against thick paper (camber angle is 0 °), paper. It is obtained by transferring to.
Rotate the tire by 72 ° in the circumferential direction and transfer it at 5 points. That is, the ground contact shape is obtained 5 times.
For the five ground contact shapes, the average value of the maximum lengths in the tire axial direction is L, and the average value of the lengths in the direction orthogonal to the axial direction is W.
The land ratio is calculated by the average area / (L × W) × 100 (%) of the five grounded shapes (black portions) transferred from the cardboard.
Here, the average value of the length and the area is a simple average of the five values.

The tread in the tire may be provided with a groove continuous in the tire circumferential direction and / or a groove discontinuous in the tire circumferential direction. Examples of the pattern having such a groove include a rib type, a lug type, a rib lug type, and a block type.

The present invention will be specifically described based on Examples, but the present invention is not limited thereto.

(Manufacturing Example 1)
Hexane, 1,3-butadiene, styrene, tetrahydrofuran and ethylene glycol diethyl ether were charged into a nitrogen-substituted autoclave reactor. Next, bis (diethylamino) methylvinylsilane and n-butyllithium were added as cyclohexane solution and n-hexane solution, respectively, and polymerization was started.
The stirring speed was 130 rpm, the temperature inside the reactor was 65 ° C., and copolymerization of 1,3-butadiene and styrene was carried out for 3 hours while continuously supplying the monomers into the reactor. Next, the obtained polymer solution was stirred at a stirring speed of 130 rpm, N- (3-dimethylaminopropyl) acrylamide was added, and the reaction was carried out for 15 minutes. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping and dried by a heat roll adjusted to 110 ° C. to obtain modified styrene-butadiene rubber (SBR).

(Production Example 2) Synthesis of Polymer 1 (Epoxide / Allyl Glycydyl Ether Copolymer) 500 mL of diethyl ether was added to a nitrogen-substituted glass flask, the internal temperature was cooled to 0 ° C. or lower, and then 0.55 mol / L. 10 mL of the triisobutylaluminum / hexane solution was added, and then a 0.55 mol / L ethanol / diethyl ether solution was added dropwise so that the internal temperature did not exceed 10 ° C. Next, a solution prepared by mixing ethylene oxide and allyl glycidyl ether so as to have a molar ratio of 9/1 and a total weight of 200 g was added dropwise so that the internal temperature did not exceed 10 ° C., and then the mixture was stirred for 8 hours. Next, the solvent was distilled off under reduced pressure at an external temperature of 50 ° C./internal pressure of 1.0 kPa or less, the remaining residue was suspended in water, filtered, and the filtered residue was washed with THF, and then 50 ° C./ Dry under reduced pressure at 1 kPa or less until a constant amount is reached, and in an 80% yield, polymer 1 (ether group derived from the above formula (A) and carbon-carbon derived from the above formula (B) in the infrared absorption spectrum). A peak was confirmed. The weight average molecular weight (Mw) was 780,000, and the content of the group (structural unit) represented by the above formula (B) in 100 mol% of the polymer was 8 mol%).

(Production Example 3) Synthesis of Polymer 2 (Amine / Allylglycidyl Ether Copolymer) Except that the ethylene oxide was changed to triglycidylamine, the same procedure as in Production Example 2 was carried out to obtain 80% yield. Polymer 2 of glycidylamine and allylglycidyl ether (The same analysis as in Production Example 2 was performed to confirm the absorption of amine and the peak derived from the carbon-carbon double bond. The weight average molecular weight was 980,000, and the above in 100 mol% of the polymer. The content of the group (structural unit) represented by the formula (B) was 8 mol%).

(Production Example 4) Synthesis of Polymer 3 (silyl-allyl glycidyl ether copolymer) 80% yield by the same procedure as in Production Example 2 except that the ethylene oxide was changed to triethoxysilyl glycidyl ether. Polymer 3 of triethoxysilyl glycidyl ether and allyl glycidyl ether (the same analysis as in Production Example 2 was performed to confirm the absorption of silanol and the peak derived from the carbon-carbon double bond. The weight average molecular weight was 640,000 and the polymer was 100 mol. The content of the group (structural unit) represented by the above formula (B) in% was 8 mol%).

In addition, the following evaluations were performed on the obtained polymers 1 to 3.

<Measurement of water insoluble matter>
Weigh 1 g of polymer in a glass flask, pour 10 mL of water, stir for 10 minutes at an internal temperature of 66 ° C, continue stirring until the internal temperature drops to 25 ° C or less, and then filter with a filter paper of material cellulose and mesh size 5C. Then, the residue remaining on the filter paper was dried at a temperature of 80 ° C. and an internal pressure of 0.1 kPa or less for 8 hours, the weight was measured, and the water-insoluble content was calculated by the following formula.
Water insoluble content (% by mass) = dry weight of residue (g) / initial weight of polymer (g) x 100

<Measurement of THF insoluble matter>
Weigh 1 g of polymer into a glass flask, pour 10 mL of tetrahydrofuran, stir at an internal temperature of 66 ° C. for 10 minutes, continue stirring until the internal temperature drops to 25 ° C. or lower, and then filter with a filter paper of material cellulose and mesh size 5C. Then, the residue remaining on the filter paper was dried at a temperature of 80 ° C. and an internal pressure of 0.1 kPa or less for 8 hours, the weight was measured, and the THF insoluble content was calculated by the following formula.
THF insoluble content (% by mass) = dry weight of residue (g) / initial weight of polymer (g) x 100

Hereinafter, various chemicals used in Examples and Comparative Examples will be collectively described.
SBR: SBR synthesized by the above method (modified S-SBR, styrene content: 25% by mass, vinyl content: 59 mol%, non-oil-extended product)
BR: BR150B manufactured by Ube Industries, Ltd. (cis amount: 97% by mass)
NR: TSR20
Polymer 1: Polymer 1 synthesized by the above method (water insoluble content: 96% by mass, THF insoluble content: 96% by mass)
Polymer 2: Polymer 2 synthesized by the above method (water insoluble content: 82% by mass, THF insoluble content: 96% by mass)
Polymer 3: Polymer 3 synthesized by the above method (water insoluble content: 92% by mass, THF insoluble content: 92% by mass)
Silica: ZEOSIL 1165MP (N ₂ SA: 160m ² / g) manufactured by Rhodesia
Carbon Black: Tokai Carbon Co., Ltd. Seest 9H (DBP oil absorption 115 ml / 100 g, N ₂ SA: 110 m ² / g)
Silane coupling agent: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
Oil: Process X-140 (aroma-based process oil) manufactured by Japan Energy Co., Ltd.
Resin: G90 manufactured by Nikko Kagaku Co., Ltd. (Kumaron Inden resin, softening point: 90 ° C)
Wax: Ozo Ace 0355 manufactured by Nippon Seiro Co., Ltd.
Anti-aging agent: Santoflex 13 (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (6PPD)) manufactured by Flexis Co., Ltd.
Stearic acid: Stearic acid "Camellia" manufactured by NOF CORPORATION
Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Metal Mining Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. 1: Noxeller NS (N-tert-) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Butyl-2-benzothiazolyl vulcan amide)
Vulcanization accelerator 2: Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Examples and comparative examples)
According to the formulation shown in Table 1, using a 1.7L Bunbury mixer manufactured by Kobe Steel, Ltd., chemicals other than sulfur and vulcanization accelerator are kneaded under the condition of 160 ° C for 4 minutes, and the kneaded product is kneaded. Got Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 4 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press-vulcanized under the condition of 170 ° C. for 12 minutes to obtain a vulcanized rubber composition.

The obtained vulcanized rubber composition was evaluated as follows. The results are shown in Table 1.

(Vulcanized rubber hardness (Hs))
Shore hardness of vulcanized rubber composition (test piece) by Type A durometer according to "Vulcanized rubber and thermoplastic rubber-How to determine hardness-Part 3: Durometer hardness" of JIS K6253-3 (2012). (Hs) was measured (JIS-A hardness). The measurement was performed at 25 ° C.

(Hardness when wet with water)
The vulcanized rubber composition (30 mm × 30 mm × 4 mm rectangular parallelepiped shape) was immersed in 20 ml of water at 25 ° C. for 6 hours to obtain a vulcanized rubber composition after water wetting. The hardness of the obtained vulcanized rubber composition after wetting with water was measured by the above method and used as the hardness at the time of wetting with water.

(Hardness when dried)
The vulcanized rubber composition after being wetted with water was dried under reduced pressure at 80 ° C. and 1 kPa or less until the amount became constant to obtain a dried vulcanized rubber composition. After returning the temperature of the obtained vulcanized rubber composition after drying to 25 ° C., the hardness of the vulcanized rubber composition after drying was measured by the above method and used as the hardness at the time of drying.

(Hardness when re-wet)
The dried vulcanized rubber composition (30 mm × 30 mm × 4 mm rectangular parallelepiped shape) was immersed in 20 ml of water at 25 ° C. for 6 hours to obtain a vulcanized rubber composition after re-wetting. The hardness of the obtained vulcanized rubber composition after re-wetting was measured by the above method and used as the hardness at the time of re-wetting.

(Tan δ when dried)
Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd., 70 ° C. tan δ of the vulcanized rubber composition after drying was measured. The measurement conditions are as follows.
Measurement temperature 70 ° C, initial strain 10%, dynamic strain 2%, frequency 10Hz

(Wet grip figure of merit)
The obtained unvulcanized rubber composition sheet is formed into a tread shape, laminated with other tire members, and press-vulcanized at 150 ° C./15 minutes to produce a tire for carts (tire size: 11 x 1.10-). 5) was created. The cart tires were mounted on the cart, and the test driver ran eight laps on a test course of 2 km per lap on a pre-sprinkled road surface, and the test driver evaluated the grip performance with Comparative Example 1 as 100 on a scale of 200 points.

(Dry grip performance index)
The obtained unvulcanized rubber composition sheet is formed into a tread shape, laminated with other tire members, and press-vulcanized at 150 ° C./15 minutes to produce a tire for carts (tire size: 11 x 1.10-). 5) was created. The cart tire was attached to the cart, and the test driver ran 8 laps on a test course of 2 km per lap on a dry road surface, and the test driver evaluated the grip performance with Comparative Example 1 as 100 on a scale of 200 points.

From Table 1, the examples in which the hardness changes reversibly with water and satisfies the above equations (1) and (2) are the total performance of wet grip performance and dry grip performance (wet grip performance and dry grip performance). It was found that (represented by the sum of the indexes) can be improved.

(Making tires)
The obtained unvulcanized rubber composition is formed into a tread shape (thickness of the tread shown in Table 2), laminated with other tire members, and press-vulcanized at 170 ° C./12 min to test tire (size). 195 / 65R15) was prepared.

(Wet grip figure of merit)
The test tires were mounted on the vehicle, and the test driver ran eight laps on a test course of 2 km per lap in which water was sprinkled on the road surface in advance, and the grip performance was evaluated by the test driver with a maximum of 200 points, with Example 2-1 as 100. The evaluation results are shown in Table 2.

(Dry grip performance index)
The test tires were mounted on the vehicle, and the test driver ran eight laps on a test course of 2 km per lap on a dry road surface, and the test driver evaluated the grip performance with Example 2-1 as 100 on a scale of 200 points. The evaluation results are shown in Table 2.

From Table 2, tires having a tread whose hardness is reversibly changed by water and which is composed of a rubber composition satisfying the above formulas (1) and (2) and whose tread thickness is 4 mm or more are wet. It was found that the total performance of the grip performance and the dry grip performance (expressed by the sum of the two indexes of the wet grip performance and the dry grip performance) can be improved more preferably.

(Making tires)
The obtained unvulcanized rubber composition is formed into a tread shape (land ratio shown in Table 3), laminated with other tire members, and press-vulcanized at 170 ° C./12 minutes to test tire (size:: 195 / 65R15) was prepared.

(Measurement of land ratio)
The land ratio (%) was measured using the JATTA standard according to the land ratio measuring method described in the present specification. The measurement results are shown in Table 3.

(Wet grip figure of merit)
The test tires were mounted on the vehicle, and the test driver ran eight laps on a test course of 2 km per lap in which water was sprinkled on the road surface in advance, and the test driver evaluated the grip performance with Example 3-1 as 100 on a scale of 200 points. The evaluation results are shown in Table 3.

(Dry grip performance index)
The test tires were mounted on the vehicle, and the test driver ran eight laps on a test course of 2 km per lap on a dry road surface, and the test driver evaluated the grip performance with Example 3-1 as 100 on a scale of 200 points. The evaluation results are shown in Table 3.

From Table 3, tires having a tread whose hardness is reversibly changed by water and composed of a rubber composition satisfying the above formulas (1) and (2) and having a land ratio of the tread of 30% or more , It was found that the total performance of wet grip performance and dry grip performance (expressed by the sum of the two indexes of wet grip performance and dry grip performance) can be improved more preferably.

Claims

A rubber composition whose hardness is reversibly changed by water and satisfies the following formulas (1) and (2).
Hardness when dried-Hardness when wet with water ≥ 1 (1)
(In the formula, the hardness is the JIS-A hardness of the rubber composition at 25 ° C.).
70 ° C tan δ ≧ 0.18 when dry (2)
(In the equation, tan δ at 70 ° C is the loss tangent measured under the conditions of 70 ° C, initial strain 10%, dynamic strain 2%, and frequency 10 Hz.)
The rubber composition according to claim 1, wherein in the formula (1), the hardness when dried-the hardness when wetted with water is 4 or more.
The rubber composition according to claim 1 or 2, wherein the tan δ at 70 ° C. at the time of drying in the formula (2) is 0.21 or more.
The rubber composition according to any one of claims 1 to 3, which comprises a hydrophilic material.
The rubber composition according to any one of claims 1 to 4, which comprises an isoprene-based rubber.
The rubber composition according to any one of claims 1 to 5, which comprises a butadiene rubber.
The rubber composition according to any one of claims 1 to 6, wherein the content of styrene-butadiene rubber in 100% by mass of the rubber component is 95% by mass or less.
A claim that satisfies the relationship of the content of styrene-butadiene rubber in 100% by mass of the rubber component> 50% by mass> the content of butadiene rubber in 100% by mass of the rubber component> the content of isoprene-based rubber in 100% by mass of the rubber component. The rubber composition according to any one of 1 to 7.
The rubber composition according to any one of claims 1 to 8, which contains 20 parts by mass or more of silica and carbon black with respect to 100 parts by mass of each rubber component.
The rubber composition according to any one of claims 1 to 9, which comprises a petroleum-based resin.
The rubber composition according to any one of claims 1 to 10, which is a rubber composition for tread.
A tire having a tire member composed of at least a part of the rubber composition according to any one of claims 1 to 11.
The tire according to claim 12, wherein the tire member is a tread, and the thickness of the tread is 4 mm or more.
The tire according to claim 12 or 13, wherein the tire member is a tread and the land ratio of the tread is 30% or more.
The tire according to any one of claims 12 to 14, wherein the tire member is a tread and has a groove continuous in the tire circumferential direction and / or a groove discontinuous in the tire circumferential direction.